Someone explain to me this contradiction of postmodernism?

The idea of no primitive and non evolved come from the basis of there is no ''superior'' but just a different. And that is what postmodernism stands for: fragmented truth. But even the idea of pos-modernism is characterized for being after modern and factually after primitive history. Even though pos-modernism stands for non primitive, it is self-promoted for thinking differently from a primitive way of think that considers the the notions of primitive and superiority accurate.